Process for explosively bonding dissimilar metals

ABSTRACT

ACCORDING TO THE PRESENT DISCLOSURE, A METAL CLADDING LAYER OF RELATIVELY LOW ACOUSTIC IMPEDANCE IS EXPLOSIVELY BONDED TO ONE SURFACE OF THE METAL OF TWO DISSIMILAR METALS WHICH HAS THE HIGHER ACOUSTIC IMPEDANCE. SUBSEQUENTLY, THE METAL CLADDING LAYER IS EXPLOSIVELY BONDED TO THE OTHER OF THE TWO DISSIMILAR METALS.

Ot. 26, 1971 H, KNQP ETAL 3,614,827

PROCESS FOR EXPLOSIVELY BONDING DISSIMILAR METALS Filed April 24. 1969 [IIIIIIIIIIIIIII I II f/z O INVENTORS, Lou/6 +14 KA/OP L/OHA/ P M94001 A/EA/ 11.5. Cl. 29470.1 4 Claims ABSTRACT OF THE DISCLOSURE According to the present disclosure, a metal cladding layer of relatively low acoustic impedance is explosively bonded to one surface of the metal of two dissimilar metals which has the higher acoustic impedance. Subsequently, the metal cladding layer is explosively bonded to the other of the two dissimilar metals.

This invention relates to explosive welding, and particularly to methods for explosively welding two dissimilar metals together.

Heretofore, bonded metal systems having dissimilar metals have been produced by explosively welding dissimilar metals together by applying an explosive charge impact to the metal having the lowest acoustic impedance. However, it is not always feasible to apply the explosive charge to the metal having lowest acoustic impedance. For example it may not be practical to apply an explosive charge to the low impedance material if it is in a confined space or if the metal having the lower acoustic impedance is too thick to sustain the detonation velocity.

It is an object to the present invention to provide a method for explosively welding dissimilar metals together wherein the explosive charge may be applied to either metal.

It is another object to the present invention to provide a method for explosively welding dissimilar metals together wherein the explosive charge is applied to the thinner of two metals.

It is another object to the present invention to provide a method of explosively welding dissimilar metals together wherein the explosive charge is applied to the metal having the higher acoustic impedance.

In accordance with the present invention, the metal having the higher acoustic impedance is cladded with a metal having a lower acoustic impedance. Preferably, the cladding metal is the same type of metal as the metal forming the other of the bimetal weld. The present invention is particularly useful for explosively welding dissimilar metals together wherein it is more convenient to apply the explosive charge to the metal having the higher acoustic impedance.

The term metal as used herein includes any elemental metal or mixture of elemental metals, for example an alloy.

The above and other features of this invention will be more fully understood in the following detailed description and the accompanying drawings, in which:

FIGS. 1 through 4 inclusive, are perspective views partly in cutaway cross-section, illustrating the method of explosively welding dissimilar metals together in accordance with the presently preferred embodiment of the present invention.

In accordance with the present invention, a sheet of material having a relatively high acoustic impedance is provided, which sheet is to be explosively welded to a sheet of relatively low acoustic material (sheet 18 in FIGS. 3 and 4). A layer 11 of explosion material is ap- 3,014, Patented D et. 26, 1971 plied to a relatively thin layer 12 of material having a relatively low acoustic impedance. Typical explosive materials suitable for use in this invention include dynamite, nitroguainidine and Du Pont Detasheet commercially available from E. I. Du Pont de Nemours & Company. Detonator 13 is applied to explosive layer 11 to be initiated by applying an electric charge to wires 14. An electric charge applied to wire 14 operates detonator 13 thereby detonating layer 11 of explosive to create a jet action behind the explosion as the detonation front moves across layer 12. Layer 12 is bonded to sheet 10 of relatively high acoustic impedance by the explosion as illustrated in FIG. 2.

During the detonation process, sheet 10 and layer 12 may be contiguous, or they may be separated by a small distance. Furthermore, it may be desirable to position sheet 10 and layer 12 at an angle to each other, which angle converges toward the edge adjacent detonator 13. By way of example, it has been found that by positioning layer 12 at an angle of about 1 to sheet 10 with the sheets spaced apart by less than about 0.035 inch at the edge nearest detonator 13, satisfactory results have been obtained.

Next, as illustrated in FIG. 3 a layer 15 of explosive material is applied to the opposite surface of sheet 10 and detonator 16 having wires 17 is attached to generator 15. Sheet 18 of relative low acoustic impedance metal is positioned adjacent or contigious or at an angle to layer 12. Preferably sheet 18 is the same metal as layer 12.

An electric charge is applied to wires 17 thereby operating detonator 16 to detonate layer 15 thereby explosively bonding thin layer 12 to sheet 18. Hence, the sheet 10 of relative high acoustic impedance metal is explosively bonded by means of thin layer 12 to sheet 18 of relatively low acoustic impedance metal.

The detonation velocity of the explosive may be any velocity suitable for obtaining bonding of the respecti e layers. By way of example, detonation velocities in the range of 2900 meters per second and 3500 meters/second have been found suitable for many metals. Of course, the detonation velocity may exceed 3500 m./sec. or be less than 2900 m./sec. for some metals.

The process according to the present invention has been performed by cladding aluminum to a sheet of 4130 steel and thereafter cladding the aluminum layer to sheet of aluminum. Of course other metal systems may be constructed in accordance with the present invention. Typically, cladding layer 12 will have a thickness in the range of about 0.002 and 0.5 inch and sheet 10 of high impedance material will have a thickness of less than about 1 inch.

The bond produced by the present invention is basically a diffusion-type bond, except that the diffusion layer does not form a straight slip plane. Hence, a mechanical bond is also achieved between the layers.

The present invention thus provides a method for explosively bonding dissimilar metals together wherein the explosive charge may be applied to the metal having the higher acoustic impedance instead of to the metal having the lower acoustic impedance material as heretofore utilized. Hence, the present invention thus provides versatility for explosive welding processes. The present invention is effective in operation and is easily performed.

This invention is not to be limited by the embodiment shown in the drawings and described in description, which is given as way of example and not of limitation, but only in accordance with the scope of the appended claims.

What is claimed is:

1. A method of bonding a first metal to a second metal, said first metal having a higher acoustic impedance than said second metal and said first and second metals being dissimilar, said method comprising the steps of covering an exposed surface of a metal cladding layer with a layer of detonating explosive, said metal cladding layer having a lower acoustic impedance than said first metal, initiating said first explosive to explosively bond the opposite surface of sad metal cladding layer to one surface of said first metal, subsequently covering the surface of said first metal opposite said one surface of said first metal which is bonded to said metal cladding layer with a layer of second detonating explosive, and initiating said second detonating explosive to explosively bond the exposed surface of said metal cladding layer to one surface of said second metal without simultaneously applying an explosive force to the surface of said second metal opposite said one surface of said second metal.

2. A method according to claim 1 wherein the metal cladding layer is constructed of the same metal as said second metal.

3. A process for producing a bonded metal system comprising a first metal and a second metal, said first metal having a higher acoustic impedance than said second metal and said first and second metals being dissimilar, said process comprising the steps of covering an exposed surface of a metal cladding layer with a layer of detonating explosive, said metal cladding layer having a lower acoustic impedance than said first metal, initiating said first explosive to explosively bond the opposite surface of said metal cladding layer to one surface of said first metal, subsequently covering the surface of said first metal opposte said one surface of said first metal which is bonded to said metal cladding layer with a layer of second detonating explosive, and initiating said second detonating explosive to explosively bond the exposed surface of said metal cladding layer to one surface of said second metal without simultaneously applying an explosive force to the surface of said second metal opposite said one surface of said second metal.

4. A process according to claim 3 wherein the metal cladding layer is constructed of the same metal as said second metal.

References Cited UNITED STATES PATENTS Re. 26,858 4/1970 Chudzik 29-4701 3,194,643 7/1965 Ma et al. 29470.1 X 3,238,071 3/1966 Holtzman 29421 E 3,281,930 11/1966 Fordharn 29470.1 3,377,693 4/1968 Fukumoto 29470.1 3,474,520 10/1969 Takizawa et al. 29-470.l

JOHN F. CAMPBELL, Primary Examiner R. J. SHORE, Assistant Examiner U .3. Cl. X.R. 29486 

